A display panel driver driving a display panel (e.g. a liquid crystal display panel) often has the function of performing image scaling to enlarge or reduce an image. Such function may be used for generating pixel data matching the display panel resolution from input image data externally fed to the display panel driver, when the input image data do not match the display panel resolution.
Since recent display panels include an increasing number of pixels, the amount of pixel data to be handled in image scaling has been increased. In the meantime, it is necessary to perform image scaling on pixel data successively fed to a display panel driver within a limited period of time. Accordingly, the processing load of an image processing unit which performs image scaling processing (typically, a scaler circuit) has been intensively increased.
One approach to address this problem is to perform image scaling processing with multiple image processing units in parallel. For example, if image scaling processing is performed on pixel data corresponding to a divisional image of a display image to be displayed in a first region of a display panel with a first image processing unit and performed on pixel data corresponding to a divisional image to be displayed in a second region of the display panel with a second image processing unit, this effectively reduces the amount of pixel data to be processed in each of the first and second image processing units.
One issue in performing image scaling with multiple image processing units is that image discontinuity may be observed in the display image at the boundary between adjacent divisional images corresponding to pixel data generated by different image processing units. Improper image processing may undesirably cause a visually-perceivable boundary between adjacent divisional images on the display panel, and this is undesired in view of image quality improvement.
Various approaches have been proposed to address discontinuity in the display image caused by image scaling using multiple image processing units in parallel. Japanese Patent Application Publication No. 2009-294273 A discloses a technique which involves dividing an image into multiple regions, detecting a motion vector of an image element which bridges adjacent two regions and performing super resolution processing using the detected motion vector.
Japanese Patent Application Publication No. 2009-296410 A discloses a technique for performing super resolution processing by using multiple super resolution processors in parallel. This patent application publication discloses a black region is disposed at a boundary at which the image is divided.
Japanese Patent Application Publication No. 2005-164347 A discloses a technique for performing super resolution processing in which an input image is divided into multiple process regions. In this technique, when divided images are synthesized, an overlapping area is disposed near the synthesizing position and the images are synthesized depending on the correlation among scattered points in the overlapping area.
Japanese Patent Application Publication No. 2009-93442 A discloses a technique which selects positions at which super resolution processing is performed on the basis of the features and visual properties of an input image.
Japanese Patent Application Publication No. 2007-193508 A discloses a technique which involves dividing an interpolation image obtained by interpolation of pixel data into multiple blocks and optimizing parameters of super resolution processing for each block by calculating the frequency components of each block.
International Publication No. WO 2014/077024 A1 discloses a technique for generating a high resolution image from low resolution multi-view images so that the high resolution image have more frequency information than each of the low resolution multi-view images, and outputting the high resolution image as an output image. In this technique, partial regions obtained by dividing the input image are analyzed to calculate the likelihood among the partial regions and necessity of super resolution processing is determined on the basis of the calculated likelihood. Super resolution processing is performed on partial regions for which supper resolution processing is determined as necessary and synthesizing processing is performed on partial regions for which supper resolution processing is not determined as necessary.
According to an inventors' study, however, the above-described techniques undesirably suffer from a problem of increased processing amount, because advanced image processing, such as image analysis and noise removal, is performed. Implementing image processing accompanied by an increased processing amount in a display panel driver undesirably increases the circuit size.